U.S. patent number 4,166,078 [Application Number 05/861,312] was granted by the patent office on 1979-08-28 for modified organopolysiloxane compositions.
This patent grant is currently assigned to SWS Silicones Corporation. Invention is credited to John C. Getson.
United States Patent |
4,166,078 |
Getson |
August 28, 1979 |
Modified organopolysiloxane compositions
Abstract
A modified organopolysiloxane composition containing in situ
generated particulate matter and a method for preparing the same
which comprises reacting an organohydrogenpolysiloxane with an
organic monomer in the presence of a free radical initiator at an
elevated temperature. The resultant composition may be combined
with vinyl containing compounds having at least two vinyl groups
per molecule and a catalyst which promotes addition of SiH groups
to vinyl groups to form elastomers.
Inventors: |
Getson; John C. (Adrian,
MI) |
Assignee: |
SWS Silicones Corporation
(Adrian, MI)
|
Family
ID: |
25335469 |
Appl.
No.: |
05/861,312 |
Filed: |
December 16, 1977 |
Current U.S.
Class: |
528/26; 525/477;
525/478; 525/479; 528/25; 528/31; 528/32; 528/33; 528/34; 556/417;
556/451 |
Current CPC
Class: |
C08F
283/12 (20130101); C08L 83/10 (20130101); C08G
77/442 (20130101) |
Current International
Class: |
C08F
283/00 (20060101); C08F 283/12 (20060101); C08G
77/00 (20060101); C08G 77/442 (20060101); C08L
83/10 (20060101); C08L 83/00 (20060101); C08L
043/04 () |
Field of
Search: |
;260/46.5H,46.5UA,827,448.2H ;204/159.13,159.15 ;528/31-34,25 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Marquis; Melvyn I.
Claims
What is claimed is:
1. A vulcanizable composition containing (A) a modified
organopolysiloxane composition which is obtained from the
polymerization of (1) a monomer having ethylenic unsaturation in
the presence of (2) an organohydrogenpolysiloxane fluid having a
viscosity of from 10 to 1,000,000 centipoise at 25.degree. C., in
which the organohydrogenpolysiloxane fluid is present in an amount
of from 20 to 95 percent by weight based on the weight of monomer
(1) and organohydrogenpolysiloxane (2) and (3) a free radical
initiator to form a composition having in-situ generated
particulate matter dispersed therein and having a polymeric organic
group which is constituted of recurring units derived from monomer
(1) grafted to the organohydrogenpolysiloxane fluid (2), said
in-situ generated particulate matter resulting from the
polymerization of monomer (1) in the presence of
organohydrogenpolysiloxane (2) and free radical initiator (3), (b)
a vinyl containing compound having at least two vinyl groups per
molecule which is capable of crosslinking with (A) and (C) a
catalyst capable of promoting the addition of silicon-bonded
hydrogen groups to silicon-bonded vinyl groups.
2. The composition of claim 1, wherein the
organohydrogenpolysiloxane fluid is present in an amount of from 25
to 70 percent by weight based on the weight of monomer (1) and
organohydrogenpolysiloxane (2).
3. The composition of claim 1, wherein the
organohydrogenpolysiloxane fluid is a hydrogen terminated
diorganosiloxane.
4. The composition of claim 1, wherein the
organohydrogenpolysiloxane fluid is represented by the formula
where R is an organic radical free of aliphatic unsaturation and is
selected from the group consisting of monovalent hydrocarbon
radicals, halogenated hydrocarbon radicals and cyanoalkyl radicals,
a has a value of from 0 to 2.5, b has a value of from 0.0005 to 2.0
and the sum of a and b is equal to 1.0 to 3.
5. The composition of claim 1, wherein the
organohydrogenpolysiloxane fluid is a copolymer having at least one
unit of the formula
and the remaining siloxane units having the formula
where R is an organic radical free of aliphatic unsaturation and is
selected from the group consisting of monovalent hydrocarbon
radicals, halogenated hydrocarbon radicals and cyanoalkyl radicals,
c has a value of 0, 1 or 2, d has a value of 1 or 2 and the sum of
c and d is equal to 1, 2 or 3 and n has a value of 0, 1, 2 or
3.
6. The composition of claim 1, wherein the
organohydrogenpolysiloxane fluid has the formula ##STR3## where R
is an organic radical free of aliphatic unsaturation and is
selected from the class consisting of monovalent hydrocarbon
radicals, halogenated monovalent hydrocarbon radicals and
cyanoalkyl radicals and m has a value sufficient to provide a
viscosity of from 10 to 1,000,000 centipoise at 25.degree. C.
7. The composition of claim 1, wherein the polymeric organic group
is constituted of recurring units derived from at least two
monomers having ethylenic unsaturation.
8. The composition of claim 7, wherein at least one of the monomers
is a non-conjugated polyolefinic monomer.
9. The composition of claim 1, wherein the composition contains an
inorganic filler.
10. The cured composition of claim 1.
11. The composition of claim 1, wherein the vinyl containing
compound is a vinylorganopolysiloxane.
12. The composition of claim 11, wherein the
vinylorganopolysiloxane is represented by the formula
where R is an organic radical free of aliphatic unsaturation and is
selected from the group consisting of monovalent hydrocarbon
radicals, halogenated monovalent hydrocarbon radicals and
cyanoalkyl radicals, R' is a vinyl group, a has a value of from 0
to 2.5, b has a value of from 0.0005 to 2.0 and the sum of a and b
is from 1.0 to 3.
13. The composition of claim 11, wherein the
vinylorganopolysiloxane is a copolymer having at least one siloxane
unit of the formula
and the remaining siloxane units have the formula
where R is an organic radical free of aliphatic unsaturation and is
selected from the group consisting of monovalent hydrocarbon
radicals, halogenated hydrocarbon radicals and cyanoalkyl radicals,
R' is a vinyl radical, c has a value of 0, 1 or 2, d has a value of
1 or 2 and the sum of c and d is equal to 1, 2 or 3 and n has a
value of 0, 1, 2 or 3.
14. The composition of claim 11, wherein the
vinylorganopolysiloxane is represented by the formula ##STR4##
where R is an organic radical free of aliphatic unsaturation and is
selected from the group consisting of monovalent hydrocarbon
radicals, halogenated monovalent hydrocarbon radicals and
cyanoalkyl radicals and y has a value sufficient to provide a
viscosity of from 10 to 750,000 centipoise at 25.degree. C.
15. The composition of claim 14, wherein R is an alkyl radical.
16. The composition of claim 15 where R is a methyl radical.
17. A process for preparing a vulcanizable modified
organopolysiloxane composition which comprises (A) preparing a
modified organopolysiloxane composition by polymerizing (1) a
monomer having ethylenic unsaturation in the presence of (2) an
organohydrogenpolysiloxane fluid having a viscosity of from 10 to
1,000,000 centipoise at 25.degree. C. in which the
organohydropolysiloxane is present in an amount of from 20 to 95
percent by weight based on the weight of the monomer (1) and
organohydrogenpolysiloxane (2) and (3) a free radical initiator to
form a modified organopolysiloxane composition having in-situ
generated particulate matter dispersed therein and having a
polymeric organic group which is constituted of recurring units
derived from the monomer (1) grafted to the
organohydrogenpolysiloxane fluid, said in-situ generated
particulate matter resulting from the polymerization of monomer (1)
in the presence of organohydrogenpolysiloxane (2) and free radical
initiator (3), and thereafter (B) adding a vinyl containing
compound having at least two vinyl groups per molecule which is
capable of crosslinking with (A) and (C) a catalyst capable of
promoting the addition of silicon-bonded hydrogen groups to
silicon-bonded vinyl groups.
18. The process of claim 17, wherein the polymerization is
conducted at a temperature of from 50.degree. to 160.degree. C.
19. The process of claim 17, wherein the polymerization is
conducted in the presence of a liquid medium which is inert with
the polymerization components and the polymerization products at
the polymerization temperature.
20. The process of claim 17, wherein the polymerization is
conducted in the presence of an organic peroxide.
Description
This invention relates to modified organopolysiloxanes,
particularly to organopolysiloxane compositions containing in situ
generated particulate matter. More particularly this invention
relates to cured organopolysiloxanes having improved physical
properties and to a method for preparing same.
BACKGROUND OF THE INVENTION
Modified organopolysiloxanes have been prepared heretofore by
reacting monomers containing aliphatic unsaturation with
organopolysiloxanes containing terminal hydroxyl or hydrolyzable
groups in the presence of free radicals as shown in U.S. Pat. Nos.
3,555,109 and 3,776,875 to Getson. Also U.S. Pat. No. 3,631,087 to
Lewis describes a process for preparing modified
organopolysiloxanes by gradually adding a mixture of monomers and
free radical initiators to preheated organopolysiloxanes. U.S. Pat.
No. 3,694,478 to Adams et al discloses a process for preparing
modified organopolysiloxanes by the gradual addition of free
radical initiators to a preheated mixture containing an
organopolysiloxane and an organic monomer having aliphatic
unsaturation. U.S. Pat. No. 4,032,499 to Kreuzer et al describes a
process for preparing modified organopolysiloxanes by reacting
monomers containing aliphatic unsaturation with organopolysiloxanes
containing hydrolyzable or hydroxyl groups in the presence of free
radical initiators and an inert liquid having a boiling point up to
about 100.degree. C. at 760 mm Hg (abs.), in which the inert liquid
is a nonsolvent for the organopolysiloxanes and the resultant
reaction product at the polymerization temperature. Polyolefin
filled vinylorganopolysiloxane compositions which are prepared by
polymerizing monomers having aliphatic unsaturation in the presence
of vinylorganopolysiloxanes and free radical initiators are
described in U.S. Pat. No. 4,014,851 to Bluestein.
Although organopolysiloxane elastomers have been used in various
industrial applications because of their thermal stability,
dielectric properties and resistance to atmospheric deterioration,
it has been found that in certain applications there
organopolysiloxane elastomers do not have the desired properties.
Attempts to improve the physical properties by adding reinforcing
fillers or agents, such as polytetrafluoroethylene fibers, have not
improved the physical properties to the desired degree. For
example, when polytetrafluoroethylene fibers have been dispersed in
a random manner in an organopolysiloxane, it was found that it was
difficult to form a homogeneous mixture. Also, it has been found
that the modified organopolysiloxanes prepared heretofore have a
tendency to shrink during curing. This property is especially
undesirable when the composition is used as a molding or potting
composition.
Therefore, it is an object of this invention to provide
organopolysiloxane compositions containing in situ generated
particulate matter. Another object of this invention is to provide
a method for preparing modified organopolysiloxanes containing in
situ generated particulate matter. Still another object of this
invention is to prepare modified organopolysiloxanes by reacting
SiH containing organopolysiloxanes with monomers containing
aliphatic unsaturation in the presence of free radical initiators.
A further object of this invention is to provide curable
organopolysiloxanes containing in situ generated particulate
matter. A still further object of this invention is to provide
elastomeric compositions having improved physical properties.
SUMMARY OF THE INVENTION
The foregoing objects and others which will become apparent from
the following description are accomplished by polymerizing organic
monomers or low molecular weight polymers having aliphatic
unsaturation with SiH containing organopolysiloxanes in the
presence of free radical initiators at an elevated temperature to
form a composition containing in-situ generated particulate matter.
The resultant composition can be combined with a vinyl containing
compound having at least two vinyl groups per molecule and a
catalyst which promotes the addition of SiH groups to vinyl groups
to form elastomers.
DETAILED DESCRIPTION OF THE INVENTION
Organopolysiloxanes having at least two SiH groups per molecule
which may be used in the practice of this invention may be
represented by the average unit formula
where R is an organic radical free of aliphatic unsaturation and is
selected from monovalent hydrocarbon radicals, halogenated
monovalent hydrocarbon radicals, and cyanoalkyl radicals, a has a
value of from 0 to 2.5 and preferably from 0.5 to 2.1 and b has a
value of from 0.0005 to 2.0 and the sum of a and b is equal to form
1.0 to 3.
Examples of suitable monovalent hydrocarbon radicals are alkyl
radicals having from 1 to 18 carbon atoms, such as methyl, ethyl,
propyl, butyl, hexyl, octyl, decyl and octadecyl radicals;
cycloalkyl radicals such as the cyclopentyl and cyclohexyl
radicals; aryl radicals such as the phenyl and naphthyl radicals;
alkaryl radicals such as the benzyl radical, the alpha, beta
phenyl-ethyl radicals and the alpha, beta phenyl-propyl radicals;
halogenated derivatives of the aforesaid radicals including
chloromethyl, trifluoromethyl, chloropropyl, chlorophenyl,
dibromophenyl, tetrachlorophenyl and difluorophenyl radicals; and
cyanoalkyl radicals such as beta cyanoethyl, gamma-cyanopropyl and
beta-cyanopropyl. It is preferred that the R groups in Formula I
have from 1 to 3 carbon atoms and more preferably that R be a
methyl radical. Formula I is intended to include those materials
wherein the R groups are mixtures of the aforesaid radicals. For
purposes of this invention, the SiH containing organopolysiloxanes
represented by Formula I above have a viscosity in the range of
from 10 to 10,000,000 centipoise at 25.degree. C., and more
preferably from 50 to 5,000,000 centipoise at 25.degree. C.
It is understood, that Formula I is intended to include
organohydrogenpolysiloxanes which have terminal SiH groups or
contain SiH groups along the chain or which are SiH terminated and
also contain SiH groups along the chain. It is preferred that the
organohydrogenpolysiloxanes contain at least two silicon bonded
hydrogen groups per molecule, especially if the resultant
composition is to be converted to an elastomer.
The organohydrogenpolysiloxanes may also be copolymers which
contain at least one unit per molecule of the formula:
where R is the same as above, c has a value of 0, 1 or 2, d has a
value of 1 or 2 and the sum of c and d is equal to 1, 2 or 3 and
the remaining siloxane units in the organopolysiloxane being units
of the formula
where R is the same as above and n has a value of 0, 1, 2 or 3.
Thus where the organohydrogenpolysiloxane is a copolymer having
siloxane units within the scope of Formula II and siloxane units
within Formula III, the copolymer generally contains from 0.1 to
99.5 mol percent of units within the scope of Formula II and from
0.5 to 99.9 mol percent of units within the scope of Formula
III.
Siloxane units within the scope of Formula II are hydrogen siloxane
units (H SiO.sub.1.5), methyl hydrogen siloxane units (H Si
Ch.sub.3 O), dimethyl hydrogen siloxane units and dihydrogen
siloxane units (H.sub.2 SiO).
A preferred class of organohydrogenpolysiloxanes within the scope
of Formula I above are those referred to as SiH terminated
diorganopolysiloxanes, such as for example those having the general
formula ##STR1## where R is the same as above and m has a value
sufficient to provide a viscosity of from 10 to 1,000,000
centipoise at 25.degree. C. It is preferred that the R groups be
methyl groups. Suitable organohydrogenpolysiloxanes are disclosed
in U.S. Pat. Nos. 2,823,218, 3,159,662 and 3,220,972.
Specific examples of organohydrogenpolysiloxanes within the scope
of Formula I above are 1,3-dimethyldisiloxane,
1,1,3,3-tetramethyldisiloxane as well as higher polymers containing
up to 100,000 silicon atoms per molecule.
Any polymerizable organic monomer having aliphtic unsaturation may
be polymerized with the organohydrogenpolysiloxanes. Examples of
suitable organic monomers are low molecular weight straight-chain
hydrocarbons such as ethylene, propylene, butylene; vinyl halides
such as vinyl chloride and vinyl fluoride; vinyl esters of organic
acids such as vinyl acetate; styrene, ring-substituted styrenes and
other vinyl aromatics such as vinylpyridine and vinylnaphthalene;
acrylic acid and derivatives of acrylic acid including the salts,
esters, amides and acrylonitrile; N-vinyl compounds such as
N-vinylcarbazole, N-vinylpyrrolidone and N-vinylcaprolactam; and
vinyl silicon compounds such as vinyltriethoxysilane.
Disubstituted ethylenes of the type CH.sub.2 .dbd.CX.sub.2 may be
used including vinylidene fluoride, vinylidene chloride, vinylidene
cyanide, methacrylic acid and compounds derived therefrom such as
the salts, esters and amides as well as methacrolein,
methacrylonitrile and the like.
Examples of disubstituted ethylenes of the type CHX.dbd.CHX such as
vinylene carbonate and various monomers which polymerize best in
the presence of other monomers, e.g. maleic anhydride, esters of
maleic and fumaric acids, stilbene, indene and coumarone may be
used in the formation of the polymeric compositions of this
invention.
Other monomers which may be employed in the polymerization are
polyfunctional olefinic monomers, i.e., having at least two
olefinic linkages, are esters such as allyl methacrylate, allyl
acrylate, diallyl adipate, methallyl acrylate, methallyl
methacrylate, vinyl acrylate, vinyl methacrylate, hydrocarbons such
as divinylbenzene and vinyl cyclohexane; polyol esters of acrylic
and methacrylic acid, e.g., ethylene dimethacrylate, tetramethylene
diacrylate and pentaerythritol tetramethacrylate and conjugated
diolefins such as 1,3-butadiene, isoprene and chloroprene.
These monomers may be used singly or in combinations of two or
three or even more. The properties of the reaction product, of
course, depend on the nature and identify of the monomeric material
as well as on the amounts used relative to the
organohydrogenpolysiloxanes. Monomers that give elastomeric
homopolymers generally provide elastomeric reaction products while
those that give plastic homopolymers tend to yield products which
are less elastic.
The reaction is most expeditiously effected by using a free-radical
initiator, normally organic peroxides, although other free-radical
initiators such as azo-compounds in which both the N atoms of the
azo linkage are attached to a tertiary carbon atom and the
remaining valences of the tertiary carbon atom are satisfied by
nitrile, carboxylalkyl, cycloalkylene or alkyl radicals, preferably
having from 1 to 18 carbon atoms. In addition to the above
mentioned initiators, ionizing radiation may also be used to bring
about the formation of free radicals.
The most suitable peroxide initiators are compounds of the formula
ROOH or compounds of the formula ROOR in which R is an organic
radical. Specific examples of peroxides which are operative in this
invention are hydroperoxides such as t-butyl hydroperoxide, cumene
hydroperoxide, decaline hydroperoxide; dialkyl peroxides such as
di-t-butyl and dicumyl peroxide; cyclic peroxides such as
ascaridole and 1,5-dimethylhexane-1,5-peroxide and peresters such
as t-butyl perbenzoate, t-butyl peroxyisopropylcarbonate and t-
butyl peroctoate; ketone peroxides such as acetone peroxide and
cyclohexanone peroxide are also applicable.
Acyl peroxides and peracids may be used in the practice of this
invention, but in general they result in less grafting, i.e., poor
yields of the grafted product. The difference is believed to lie in
the nature of the radicals produced. Thus tertiary alkoxy radicals
from di-t-butyl peroxide, for example have a tendency to abstract
hydrogen atoms from the organic groups linked to the silicon atoms,
which is a possible mechanism in grafting. On the other hand,
acyloxy radicals produced from an acyl peroxide e.g., benzoyl
peroxide, while effective polymerization initiators are relatively
ineffective in abstracting hydrogen atoms from the organic groups
linked to the silicon atoms.
The amount of free-radical initiator employed is not critical and
as little as 0.05 percent of the more active peroxide initiators
based on the weight of the monomer is generally adequate in most
cases. However, where it is desirable to increase the reaction
rate, then as much as 3 percent or even more of the initiator may
be used. As a general rule, it is advisable not to exceed about 5
percent concentration, since higher concentrations tend to promote
cross-linking and thus cause an undesirable increase in the
viscosity of the reaction mixture.
These free radical initiators can be employed with any monomer
desired. When, for example, the half-life of the free radical
initiator in toluene is more than 2 hours at the polymerization
temperature, then a portion of the total amount or all of the free
radical initiator can be mixed with the organohydrogenpolysiloxane
and monomer containing aliphatic unsaturation. However, if the
half-life of the free radical initiator in toluene is less than 2
hours at the polymerization temperature, then it is preferred that
the free radical initiator be added in increments or continuously
during the polymerization.
The organohydrogenpolysiloxanes may be polymerized with the
monomers containing aliphatic unsaturation in the absence or
presence of a liquid medium which is inert or nonreactive with the
polymerization components, the polymerization products as well as
in situ generated particulate matter. It is preferred that the
liquid medium have a boiling point below about 130.degree. C. at
760 mm Hg (abs.) and be a nonsolvent for polymers obtained as a
result of the polymerization at the polymerization temperature.
Examples of suitable inert liquids which may be employed are water,
methanol and saturated aliphatic hydrocarbons, aliphatic fluoro and
chloro hydrocarbons in which three halogen atoms are linked to at
least one carbon atom. Water is the preferred inert liquid, since
it is readily available and the organohydrogenpolysiloxane, monomer
and the polymer obtained from the polymerization reaction are
insoluble therein.
Also, it is possible to use a mixture consisting of several liquids
having a boiling point below about 130.degree. C. at 760 mm Hg
(abs.) which are inert to the polymerization reactants and the
polymer resulting therefrom at the polymerization temperature.
Although the temperature of the polymerization reaction is not
critical, it has been found that temperatures above about
160.degree. C. may in some cases prevent the generation of
particulate matter, and thus provide a polymer having inferior
properties. Consequently, it is preferred that the copolymerization
be conducted at temperatures below about 150.degree. C., and more
preferably at a temperature of from about 50.degree. C. to about
140.degree. C.
It is preferred that the polymerization reaction be carried out in
a substantially oxygen-free environment because of the free radical
nature of the reaction. This can be accomplished by sweeping the
reaction vessel with an inert gas such as nitrogen.
The polymerization reaction can be carried out at subatmospheric,
atmospheric or superatmospheric pressure. Preferably the
copolymerization reaction is carried out at atmospheric pressure.
Depending on the particular conditions employed, the polymerization
reaction is generally completed in from 30 minutes up to about 10
hours.
The proportion of organic monomers to organohydrogenpolysiloxanes
may be varied within wide limits. Thus, the
organohydrogenpolysiloxane concentration may range from about 20 to
95 percent based on the weight of the organic monomers and
organohydrogenpolysiloxane. Even though the proportion of
organohydrogenpolysiloxanes may be below about 20 percent by weight
based on the weight of the reactants, it is preferred that the
organohydrogenpolysiloxane concentration be from about 25 to 70
percent based on the total weight of the reactants.
It has been found that the shear rate may have a substantial
influence on the formation of the particulate matter, especially
the formation of elongated rodlike particles. It is believed that
by controlling the amount of shear exerted on the reactants,
particles are formed which take on different configurations. For
example, elongated rodlike particles of from 10 to 500 microns in
length and from 1 to 5 microns in diameter are generated in situ by
carefully controlling the shear rate. Also, it has been found that
these rodlike particles greatly improve the physical properties of
the resultant organopolysiloxane composition, especially the cured
polymers. Consequently, it is preferred that elongated rodlike
particles be generated in order to impart improved physical
properties to the resultant polymer. For example, where
organopolysiloxane compositions containing rodlike structures are
cured to form elastomeric materials, resultant elastomers exhibit
improved tensile strength, elongation and tear strength values.
Since the shear rate may have a profound influence on the size and
shape of in situ generated particles, it is preferred that the
shear rate be in the range of from about 5 to 1,000 sec..sup.-1 and
more preferably from about 15 to 300 reciprocal seconds. The shear
rate is calculated as the linear speed of the impeller divided by
its distance from the reactor wall at the point of its closest
contact.
The products of this invention may be separated from the unreacted
monomers by any conventional technique known in the art, such as by
distillation, solvent extraction or selective solvent
fractionation.
The modified organopolysiloxane compositions obtained from the
polymerization reaction of the present invention include
organohydrogenpolysiloxanes in which some or all of the organic
polymer is grafted to the organopolysiloxane chain through a
carbon-to-carbon linkage and mixtures of organic homopolymers,
copolymers and organohydrogenpolysiloxanes.
The modified organopolysiloxane compositions of this invention are
useful in the preparation of elastomers, sealants, potting
compounds and as coatings. Also, these compositions are useful as
molding compositions, especially where it is desired to keep
shrinkage to a minimum.
These modified organopolysiloxane compositions may be used in the
preparation of room temperature and heat vulcanizable elastomers.
Generally these room temperature and heat vulcanizable compositions
contain (1) the modified organohydrogenpolysiloxane composition
whose preparation is described above, (2) a compound having at
least two vinyl groups per molecule as a crosslinking agent and (3)
a catalyst which promotes the addition of the SiH group of the
organohydrogenpolysiloxane to the vinyl group of the
vinylorganopolysiloxane.
Vinyl containing compounds which may be used as crosslinking agents
in the present invention are vinyl containing organopolysiloxanes.
These vinyl containing organopolysiloxanes are well known and have
the average unit formula
in which R is the same as above, R' is a vinyl group, i.e.,
CH.sub.2 .dbd.CH--, linked to the silicon atom by a silicon-carbon
linkage, a has a value of from 0 to 2.5, preferably from 0.5 to
2.1, b has a value of from 0.0005 to 2.0, and the sum of a and b is
equal to 1.0 to 3. Suitable vinylorganopolysiloxanes are disclosed
for example in U.S. Pat. Nos. 3,159,662 and 3,220,972.
In Formula IV the R radicals which may be the same or different are
monovalent hydrocarbon radicals having from 1 to 18 carbon atoms,
halogenated hydrocarbon radicals and cyanoalkyl radicals.
Preferably, each R radical in Formula IV is a methyl radical.
The vinylorganopolysiloxanes represented by Formula IV above have a
viscosity of from about 10 to about 750,000 centipoise at
25.degree. C. and more preferably from about 100 to 150,000
centipoise at 25.degree. C.
It is to be understood that Formula IV is intended to include
organopolysiloxanes which are vinyl terminated or contain the vinyl
groups along the chain or which are vinyl terminated and also
contain vinyl groups along the chain.
Preferred vinylorganopolysiloxanes within the scope of Formula IV
are vinyl terminated diorganopolysiloxanes having the general
formula ##STR2## in which R is the same as above and y has a value
sufficient to provide a viscosity of from about 10 to 750,000
centipoise at 25.degree. C. Vinyl terminated diorganopolysiloxanes
are well known as illustrated by U.S. Pat. No. 3,436,366.
Specific examples of vinylorganopolysiloxanes within the scope of
Formula IV are vinylpentamethyldisiloxane,
1,3-divinyltetramethyldisilosane,
1,1,3-trimethyl-1,3,3-trivinyldisiloxane,
1,1,3,3-tetravinyldimethyldisiloxane as well as higher polymers
containing up to 100,000 or more silicon atoms per molecule. Also
included in Formula IV are cyclic siloxanes containing silicon
bonded vinyl groups such as the cyclic trimer, tetramer or pentamer
of methylvinyl siloxane [(CH.sub.2 .dbd.CH)(CH.sub.3) SIO]. The
preferred cyclic siloxane is the
tetramethyltetravinylcyclotetrasiloxane.
The vinylorganopolysiloxanes represented by Formula IV may also be
copolymers having (1) siloxane unit of the formula
where R and R' are the same as above, c has a value of 0, 1 or 3, d
has a value of 1 or 2 and the sum of c and d is equal to 1, 2 or 3
and (2) an organopolysiloxane represented by Formula III above.
Thus, when the vinylorganopolysiloxane employed herein is a
copolymer having siloxane units within the scope of Formula V with
units within the scope of Formula III, the copolymer generally
contains from 1.0 to 99.5 mol percent of units within the scope of
Formula V and from 0.5 to 99.9 mol percent of units within the
scope of Formula III.
Also, included among the vinylorganopolysiloxanes are those
polysiloxane compositions containing mixtures of
organopolysiloxanes containing vinyl groups.
Other vinyl containing compounds which may be employed as
crosslinking agents are organic compounds having at least two
nonconjugated olefinic linkages. Examples of suitable compounds are
esters, such as allyl methacrylate, allyl acrylate, diallyl
adipate, methallyl acrylate, methallyl methacrylate, vinyl acrylate
and vinyl methacrylate; esters, such as divinyl ether of diethylene
glycol, hydrocarbons, such as divinylbenzene and vinylcyclohexene;
polyol esters of acrylic acid and methacrylic acid, e.g., ethylene
dimethacrylate, tetramethylene diacrylate, 1,3-butylene
dimethacrylate, trimethylolpropane trimethacrylate and
pentaerythritol tetramethacrylate.
The catalyst employed in the vulcanizable compositions of this
invention may be any of the platinum compounds or platinum
containing complexes which promote the addition of silicon bonded
hydrogen atoms to silicon bonded vinyl groups. Examples of suitable
platinum compounds are chloroplatinic acid, platinum deposited on
carriers such as silica gel or powdered charcoal, salts of
platinum, the reaction products of chloroplatinic acid and
alcohols, aldehydes and ketones, platinum-siloxane complexes,
platinum-olefin complexes, platinum carboxylates, nitrile-platinum
halide complexes, ammonium platinum complexes such as disclosed in
U.S. Pat. No. 3,795,656 to Martin and platinum complexes of
unsaturated siloxanes which are substantially free of halogen, such
as disclosed in U.S. Pat. No. 3,814,730 Karstedt. Preferably the
platinum catalyst is a platinum-ketone complex such as disclosed in
U.S. Pat. No. 3,798,252 to Nitzsche et al.
The proportions of the various ingredients employed in the practice
of the present invention can vary within wide limits and the
proportions of ingredients are not affected by the stoichiometry of
the addition reactants involved, since many of the products
prepared in accordance with this invention exhibit satisfactory
properties even though the final product may contain unreacted
vinyl groups or unreacted silicon-bonded hydrogen atoms. Generally,
the vinyl containing compound and the organohydrogenpolysiloxane
obtained from the polymerization reaction should be present in such
proportions that the reaction mixture contains from 0.005 to 20
silicon-hydrogen linkages per vinyl group. Moreover, it is
preferred that an equal number of silicon-hydrogen linkages and
vinyl groups be present in the reaction mixture to form a final
product which is free of silicon-hydrogen linkages and vinyl
groups.
The platinum catalyst is generally added to the mixture containing
the vinyl compound and the organohydrogenpolysiloxane obtained from
the polymerization reaction in an amount based on the vinyl groups
present in the composition. A satisfactory reaction will occur when
the catalyst composition is present in an amount sufficient to
provide as little as one atom of platinum per million vinyl groups
present in the vinyl containing compound. The catalyst may be
present in an amount to provide as high as one platinum atom per
thousand vinyl groups. In general, it is preferred that the
platinum catalyst be employed in an amount sufficient to provide
from one platinum atom per 1,000 to one platinum atom per 100,000
vinyl groups in the vinyl containing compound.
When employing exceptionally small quantities of the platinum
catalyst, it is often desirable to dissolve the latter in a solvent
which is inert to the reactants under the conditions of the
reaction so as to facilitate uniform dispersion or solution of the
platinum catalyst in the vinyl containing compound and the
organohydrogenpolysiloxane obtained from the polymerization
reaction. Suitable solvents include, for example, hydrocarbon
solvents such as benzene, toluene, xylene, mineral spirits,
halogenated alkanes as well as oxygenated solvents such as dioxane,
ethanol, butanol and the like. Where a diluent or solvent is
employed, the amount of the latter is not critical. Satisfactory
solutions of platinum catalysts can be prepared which contain from
0.1 to 0.0001 part of platinum catalyst per part of solvent.
The composition containing the vinyl compound and the
organohydrogenpolysiloxane obtained from the polymerization
reaction and platinum catalyst can be vulcanized at temperatures as
low as room temperature up to temperatures of the order of
100.degree. to 150.degree. C. The time required for vulcanizing the
composition can also vary over wide limits, depending upon the
particular reactants involved, the proportions of reactants and the
reaction temperature. Thus, curing can be effected in times which
vary from a few minutes up to 24 hours or more. If all other
factors are equal, the rate of reaction increases as the
temperature increases and as the concentration of the platinum
catalyst in the reaction mixture increases.
Where it is desired to store these curable compositions for a
period of time, it is preferred that these compositions be prepared
in two separate packages, which are later combined at a time when
the compositions are to be cured, i.e., converted to an elastomeric
state. In the case of a two package formulation, the
organohydrogenpolysiloxane composition prepared in accordance with
this invention and the platinum catalyst are placed in one package
and the vinyl containing compound and any other fillers or
additives are placed in the second package. These packages are
merely mixed at the point of use and the mixture cured.
While the curable compositions of the present invention are
sufficiently reinforced by the presence of the in situ generated
particulate matter, additional fillers and other additives may be
incorporated therein. Examples of suitable fillers which may be
employed in the curable compositions are fumed silicas,
high-surface-area precipitated silicas, silica aerogels as well as
coarser silicas such as diatomaceous earth, crushed quartz and the
like. Other fillers which may be used are metallic oxides such as
titanium oxide, ferric oxide, zinc oxide and fibrous fillers such
as asbestos, fibrous glass and the like. Additives such as pigments
and antioxidants and ultraviolet absorbents and the like may also
be included in these compositions.
Various embodiments of this invention are further illustrated by
the following examples in which all parts are by weight unless
otherwise specified.
PREPARATION OF MODIFIED ORGANOHYDROGENPOLYSILOXANE COMPOSITIONS
Example 1
A mixture containing 78 parts of stryene, 63 parts of butyl
acrylate, 94 parts of a hydrogen terminated dimethylpolysiloxane
having a viscosity of 50 centipoise at 25.degree. C. and an SiH
content of 0.7 percent, 1.5 parts of
1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane and 12 parts of
water are added to a 500 milliliter glass reactor equipped with a
stirrer, nitrogen inlet, reflux condenser and oil bath. The system
is flushed with nitrogen and heated to a temperature of about
97.degree. C. with agitation for about 4.3 hours and then stripped
for one hour at 100.degree. C. and for an additional hour at
120.degree. C. The viscosity of the resultant product is determined
with a Brookfield Viscometer at 25.degree. C. with a No. 7 spindle
and at 10 revolutions per minute. After one minute the viscosity is
92,000 centipoise, after five minutes, 68,000 centipoise and after
ten minutes 60,000 centipoise. The resultant product, which is a
while opaque viscous material contains elongated particulate matter
when viewed under a microscope (X430).
Example 2
A mixture containing 141 parts of styrene, 94 parts of a hydrogen
terminated dimethylpolysiloxane having a viscosity of 50 centipoise
at 25.degree. C. and an SiH content of 0.7 percent and 1.5 parts of
1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane are added to a 500
milliliter glass reactor equipped with a stirrer, nitrogen inlet,
reflux condenser and oil bath. The system is flushed with nitrogen
and heated to a temperature of about 97.degree. C. with agitation
for about 4.3 hours and then stripped for one hour at 100.degree.
C. and for an additional hour at 120.degree. C.
Example 3
A mixture containing 41 parts of styrene, 204 parts of
butylacrylate, 164 parts of a hydrogen terminated
dimethylpolysiloxane having a viscosity of 50 centipoise and an SiH
content of 0.7 percent, 1.5 parts of
1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane and 20 parts of
water are added to an 800 milliliter glass reactor equipped with a
stirrer, nitrogen inlet, reflux condenser and oil bath. The system
is flushed with nitrogen and heated to a temperature of 97.degree.
C. with agitation for about 4.3 hours and then stripped for one
hour at 100.degree. C. and for an additional hour at 120.degree.
C.
Example 4
A mixture containing 154 parts of butylacrylate, 42 parts of
acrylonitrile, 131 parts of hydrogen terminated
dimethylpolysiloxane having a viscosity of 50 centipoise at
25.degree. C. and an SiH content of 0.7 percent, 1.5 parts of
1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane and 15 parts of
water are added to a 500 milliliter glass reactor equipped with a
stirrer, nitrogen inlet, reflux condenser and oil bath. The system
is flushed with nitrogen and heated to a temperature of about
97.degree. C. with agitation for about 4.3 hours and then stripped
for one hour at 100.degree. C. and for an additional hour at
120.degree. C.
Example 5
A mixture containing 90 parts of vinylchloride, 210 parts of a
trimethylsiloxy-terminated copolymer having a viscosity of 400
centipoise at 25.degree. C. and consisting of 2 mol percent
methylhydrogensiloxane units with the remainder of the
diorganopolysiloxane units being dimethylsiloxane units and 1.5
parts of 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane are added
to a 500 milliliter glass reactor equipped with a stirrer, nitrogen
inlet, reflux condenser and oil bath. The system is flushed with
nitrogen and heated to a temperature of about 97.degree. C. with
agitation for about 4.3 hours, and then stripped for one hour at
100.degree. C. and for an additional hour at 120.degree. C.
Example 6
A mixture containing 155 parts of vinyl acetate, 145 parts of a
copolymer having a viscosity of 1,000 centipoise at 25.degree. C.
consisting of dimethylhydrogensiloxane, dimethylsiloxane,
methylhydrogensiloxane and trimethylsiloxane units in a mol ratio
of 1.9, 4.9, 3.1 and 0.1 respectively, 1 part of
tert-butylperoctoate and 12 parts of water are added to a 500
milliliter glass reactor equipped with a stirrer, nitrogen inlet,
reflux condenser and oil bath. The system is flushed with nitrogen
and heated to a temperature of about 97.degree. C. with agitation
for about 4.3 hours, and then stripped for one hour at 100.degree.
C. and for an additional hour at 120.degree. C. A white viscous
opague fluid is obtained.
Example 7
A mixture containing 150 parts of vinylidene chloride, 150 parts of
the polysiloxane fluid of Example 1, 1 part di-t-butylperoxide and
12 parts of water are added to a 500 milliliter glass reactor
equipped with a stirrer, nitrogen inlet, reflux condenser and oil
bath. The system is flushed with nitrogen and heated to a
temperature of about 97.degree. C. with agitation for about 4.3
hours, and then stripped for one hour at 100.degree. C. and for an
additional hour at 120.degree. C. A white viscous opaque fluid is
obtained.
Example 8
A mixture containing 100 parts of styrene, 82 parts of butyl
acrylate, 10 parts of allyl methacrylate, 121 parts of the
polysiloxane fluid of Example 1, 1 part of di-t-butylperoxide and
12 parts of water are added to a 500 milliliter glass reactor
equipped with a stirrer, nitrogen inlet, reflux condenser and oil
bath. The system is flushed with nitrogen and heated to a
temperature of about 97.degree. C. with agitation for about 4.3
hours, and then stripped for one hour at 100.degree. C. and for an
additional hour at 120.degree. C. A white viscous opaque product is
obtained.
Example 9
The procedure of Example 1 is repeated except that 94 parts of a
hydrogen terminated dimethylpolysiloxane having a viscosity of 350
centipose at 25.degree. C. are substituted for the polysiloxane of
Example 1. A white viscous composition is obtained.
Example 10
The procedure of Example 8 is repeated except that 150 parts of a
hydrogen terminated dimethylpolysiloxane having a viscosity of 400
centipoise at 25.degree. C. are substituted for the polysiloxane
fluid of Example 8.
Example 11
The procedure of Example 1 is repeated except that 100 parts of a
copolymer containing dimethylsiloxane, methylhydrogensiloxane and
trimethylsiloxane units having a ratio of dimethylsiloxane units to
methylhydrogensiloxane units of 12:1 and a viscosity of 3,000
centipoise at 25.degree. C. are substituted for the
methylhydrogenpolysiloxane of Example 1.
PREPARATION OF VULCANIZED COMPOSITIONS
Example 12
A mixture containing 20 parts of the modified organopolysiloxane
composition of Example 1, 0.5 part of a 0.01 percent by weight
solution of chloroplatinic acid in isopropanol and 0.5 part of
1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane cures to
an elastomeric solid overnight.
Example 13
A mixture containing 20 parts of the modified organopolysiloxane
composition of Example 1, 0.5 part of a 0.01 percent by weight
solution of chloroplatinic acid in isopropanol and 0.5 part of
1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane is heated
to 120.degree. C. and cures to an elastomeric solid in less than
one hour.
Example 14
A mixture containing 10 parts of the modified organopolysiloxane
composition of Example 1, 0.75 part of
1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane and 0.25
part of an amino-functional platinum catalyst prepared in
accordance with Example 1 of U.S. Pat. No, 3,795,656 is heated to
115.degree. C. and cures to an elastomeric solid in 8 minutes.
Example 15
The procedure of Example 14 is repeated except that 10 parts of the
modified organopolysiloxane of Example 3 is substituted for the
modified organopolysiloxane composition of Example 1. The
composition cures to an elastomeric solid when heated to
115.degree. C.
Example 16
The procedure of Example 14 is repeated except that the composition
of Example 4 is substituted for the modified composition of Example
1. An elastomer is obtained after heating to 115.degree. C. for
about 10 minutes.
Example 17
The procedure of Example 14 is repeated except that a copolymer
having a viscosity of 2,000 centipoise at 25.degree. C. and
containing 95 mol percent of dimethylsiloxane units and 5 mol
percent of methylvinylsiloxane units is mixed with the modified
organopolysiloxane of Example 8 and cured at 115.degree. C. to form
an elastomeric solid.
Although specific examples of the invention have been described
herein, it is not intended to limit the invention solely thereto,
but to include all the variations and modifications falling within
the spirit and scope of the appended claims.
* * * * *